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Forecast for the Salt Lake Area Mountains

Nikki Champion
Issued by Nikki Champion on
Wednesday morning, December 15, 2021
Today, we have a HIGH avalanche danger on all steep mid and upper elevation slopes facing west through north through east where fresh wind drifts and new snow sit atop of the weak faceted snow. There is a CONSIDERABLE danger on southerly upper elevation slopes. Stay off of and out from underneath slopes 30° degrees and steeper at the mid and upper elevations. If you trigger an avalanche, it is likely to break down 2-4' and up to several hundred feet wide.
The remaining aspects and elevations have a MODERATE danger.
There are three avalanche problems to watch for: (1) triggering a slab avalanche 2-4' deep in the weak faceted snow, (2) soft slabs of wind drifted snow that would likely steep down into the weak snow below, and (3) sluffing within the new snow.
Low
Moderate
Considerable
High
Extreme
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Weather and Snow
Currently, skies are overcast and it continues to snow. Mountain temperatures are in the low to mid-teens °F above 8,000'. Winds remain high across mid and upper elevation ridgelines blowing from the West with speeds of 10-25 mph, gusting into the 30s at mid-elevations. At upper elevation ridgelines, winds are blowing with speeds of 25-40 mph, gusting near 70 mph. Heavy snowfall began falling early last night, with snowfall rates peaking between 9 PM-Midnight, with periods of 0.20" of water an hour!
At 5 AM this morning snowfall totals are at:
Little Cottonwood Canyon: 13-19" (1.3-1.8 " H2O)
Big Cottonwood Canyon: 12-16" (1.14-1.40" H2O)
Park City Ridgeline: 7-13" (1.0-1.2" H2O)
Today, we can expect skies to remain overcast and temperatures to climb into the upper teens °F at about 8,500' in elevation. We should continue to see snowfall as the system switches to a more of an orographically forced mode. This morning, we can expect another 3-6" of snowfall, before tapering off this afternoon. Winds will remain elevated and blowing from the West. At mid-elevations winds will average 15-25 mph, with gusts up to 35 mph. At upper-elevation ridgelines winds will blow 20-30 mph, with gusts up to 50 mph.
This evening, a second wave should move into the area lasting through Friday with another 5-8" of new snow (0.40"-0.60" water).
Recent Avalanches
Ski areas reported some natural activity overnight. No new avalanches were reported to occur yesterday, but a few avalanches that occurred over the weekend continue to roll in. You can find all backcountry observations HERE.
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Avalanche Problem #1
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
Most of the avalanches we've seen over the past few days have been soft slab avalanches failing on a persistent weak layer on the Northern end of the compass. With every bump in wind speed and or new snowfall event added to our fragile snowpack, we continue to wait for the weak facets to become unglued. This morning we added two huge new stressors to this fragile snowpack in the form of new snowfall and elevated winds. We don't know if this is the tipping point that will cause the snowpack to become unglued, but we do know that the avalanche danger and likelihood of avalanches will be on the rise.
Given the new snowfall, elevated winds, and poor snowpack structure I would avoid any west through north through east facing terrain steeper than 30 degrees, with any steep terrain above or attached to it. Very dangerous avalanche conditions exist, and today is not the day to push it. Avoidance is key. Stick to low-angle terrain.
Photo: Torrey & Graves showing the weak faceted snow layer in their snowpit and hands.
Avalanche Problem #2
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
The winds have been cranking all week, and continue to remain elevated. Hidden Peak is gusting above 70 mph this morning. High winds in combination with the new snow will continue to form both soft and hard slabs at all mid and upper elevations. As the winds continue to blow, these slabs will become more firm and cohesive. This can allow you to travel out farther onto the slope before it breaks, and can fail larger and wider than expected. Look for any signs of wind drifted snow on all mid and upper elevation terrain features that snow could be easily deposited, such as ridgelines and gullies.

High winds can deposit snow on all aspects but give west through north through east extra caution, as triggering an avalanche that initially fails in the wind-drifted snow will likely break down more deeply into the weak faceted snow below.
Avalanche Problem #3
New Snow
Type
Location
Likelihood
Size
Description
This morning the Wasatch mountains have already received 10-19" of new snow. While snow totals are important, what we truly pay attention to is what RATE that snowfalls and how quickly it loads the snowpack. We call this precipitation intensity, and if those rates stay elevated or increase throughout the morning we could see new snow avalanches occurring naturally. Keep an eye on the sky, if the snow rate rapidly increases you know the danger is on the rise.
Today, you may find both fast-running sluffs and sensitive storm slabs in areas that received the most snow or in areas that also had some wind-drifting. Look for signs of new snow instabilities such as cracking, and collapsing. Triggering an avalanche that initially fails in a storm snow could easily down more deeply into the weak faceted snow.
General Announcements

This information does not apply to developed ski areas or highways where avalanche control is normally done. This forecast is from the U.S.D.A. Forest Service, which is solely responsible for its content. This forecast describes general avalanche conditions and local variations always occur.